Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
INDICATIVE, SUBJUNCTIVE
These terms apply to the mood of verbs: an indicative verb is one that makes a factual or actual statement, as contrasted with a verb in the subjunctive mood, which makes a doubtful, conditional, or hypothetical statement or one contrary to fact or in some sense subordinate to another statement. Fred wins both sets, so he is the champion has two indicative verbs, wins and is. If Fred win both sets, he will be the champion is a rather stiffly formal example of a subjunctive verb, win. The subjunctive shows up much more often today with the verbs be and have than with other verbs, as in If he be winner of both sets or If he have luck enough to win both sets, but even these sound formal. Much more common today is the use of the auxiliaries should and would (If he should win both sets …), and most common of all in many conditional statements is the indicative: If he wins [is the winner, has luck enough to win]…. All these are Standard.
It has long been conventional to observe that the inflected subjunctive is fast disappearing from English, and the statement is partly true. But particularly at the upper levels of both speech and writing the subjunctive is regularly used in Standard English, and even at the lower levels divided usage and the replacement of the subjunctive by the indicative occur only in certain grammatical situations. In conditions contrary to fact, for example, finite verbs such as arrive are rarely put into the subjunctive, except in the most careful Formal English; you’re more likely to hear If he arrives in time than If he arrive in time. But with was and were there is much more divided usage and much more argument about the appropriate usage, especially after verbs like wish: both I wish that his argument were sounder (subjunctive) and I wish that his argument was sounder (indicative) are heard and seen today in Standard English. Some relic or fossil subjunctives (if I were you, far be it from me, if need be, and the like) also continue to be Standard; to say or write If I was you is still Substandard and will be severely judged. Standard English also continues to require the subjunctive in that clauses following verbs such as move, request, command, insist, and the like: I move that the secretary cast one ballot. We suggest that the treaty be abrogated. I urged that he consult a physician.
One reason so much of the subjunctive appears to have fallen off is that only in the third person singular present tense of most finite verbs can we recognize a distinctive subjunctive form: he goes is indicative, if he go is subjunctive. Be has a couple of additional distinctive subjunctive forms: be in the present tense and were in first and third persons singular past tense. All others have been replaced either by the regular indicative forms or by the use of auxiliaries such as should.
